BVD may be shed in excretions and secretions, including nasal discharge, tears, saliva, urine, feces, milk and semen. These routes apply to both acute infections and to PI animals. BVD may be transmitted during embryo transfer, rectal examination, and artificial insemination. The virus may survive in cool, protected environments for several days; thus, susceptible animals may acquire BVD from contaminated fomites such as nose tongs, halters, milk bottle nipples, balling guns, etc. A small needle that was contaminated with fresh blood from a PI animal was used successfully to infect susceptible cattle with BVD.
Source: APHIS